linux-imx

iomap: warn on zero-length mappings

Don't let the iomap callback get away with feeding us a garbage zero
length mapping -- there was a bug in xfs that resulted in those leaking
out to hilarious effect.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>